The present invention relates to novel dye forming couplers for use, for example, in silver halide color photosensitive materials and to a silver halide color photosensitive material containing the same.
One type of silver halide color photosensitive material in which a color image is formed by making use of a reaction of a color developing agent with dye forming couplers which develop yellow, magenta and cyan is now most widely put into practical use.
In recent years, studies have been actively conducted to improve dye forming couplers for silver halide color photosensitive materials in terms of color reproducibility and stability of dye image. However, no satisfactory improvement has yet been made, due to, for example, limitations relating to the color development agent. Particularly, for cyan couplers, phenol cyan couplers or naphthol cyan couplers have heretofore continuously been employed, but dyes which are formed from these cyan couplers have undesired absorption in the blue and green regions, which is a serious obstacle to an improvement in color reproducibility. In addition, it is disadvantageous to the improvement in sharpness of the resulting images that the cyan dyes that are formed from the conventional cyan couplers have a small molar extinction coefficient.
Recently, cyan dye forming couplers with a novel skeleton having a nitrogen-containing heterocyclic ring have been actively studied, and various heterocyclic compounds have been proposed: for example, a diphenylimidazole coupler disclosed in Japanese Patent Application Laid-Open (KOKAI) No. 63-226653 (1988), and pyrazoloazole couplers disclosed in Japanese Patent Application Laid-Open (KOKAI) Nos. 63-199352 (1988), 63-250649 (1988), 63-250650 (1988), 64-554 (1989), 64-555 (1989), 1-105250 (1989), 1-105251 (1989), etc. These couplers are expressly improved in color reproducibility and are characterized by excellent absorption characteristics of the dyes formed therefrom.
The above-described conventional couplers suffer, however, from the disadvantages that the cyan dyes that are formed therefrom have absorption in the shorter wavelength region and are inferior in stability to light and heat, and further involve the serious problem in practical application that the coupling activities of the couplers themselves are low.
Dark fading of cyan dyes obtained from the above in a reducing atmosphere is reported, for example, in the Journal of NSG (Japan Society of Photography) No. 50,183 (1987).